GEOCHEMISTRY AND MAGNETIC SUSCEPTIBILITY OF UPPER DEVONIAN CATSKILL FORMATION PALEOSOLS, NORTH-CENTRAL PENNSYLVANIA

The Catskill Formation redbeds in the northern Appalachian foreland basin (north-central Pennsylvania) record Late Devonian (Famennian) terrestrial paleoclimate. Major element geochemical data from Catskill Formation paleosols preserve evidence of moderate silicate weathering (chemical index of alteration values 63-79), with an up-section increase that perhaps reflects enhanced Upper Famennian seasonality related to the onset of end-Devonian glaciation in the subtropics. To test whether this trend is consistent with a temporal shift to more humid climate conditions overall, or instead, an intensification of seasonality in the Upper Devonian, X-Ray Fluorescence (XRF) geochemical data and magnetic susceptibility (MS) data were acquired on two ~15-20 m-thick mudstone-paleosol intervals from core (Lackawanna County, Pennsylvania). Both datasets were measured at a 20-cm sampling interval with handheld XRF and MS instruments. Preliminary results show a correlation between XRF and MS records. These new data, together with companion detailed (cm-scale) stratigraphy, allow for a high-resolution evaluation of variation in the chemical weathering signal related to climatic change during the uppermost Famennian. Further analysis is necessary (1) to evaluate whether increased seasonality is consistent with pre-to-early mountain glaciation in the Appalachian hinterland, and (2) to assess the influence of geodynamic effects on the chemical weathering signal, especially given the tectonically dynamic and orogen-proximal setting of the Appalachian Basin during this time.